Production of uranium tubing



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PRODUCTION OF URANIUM TUBING Filed Nov. 50, 1944 2 Sheets-Sheet l A ril 15, 195% E. c. CREUTZ 9,

PRODUCTION OF URANIUM TUBING Filed Nov. 50, 1944 2 Sheets-Sheet 2 fiYZ/eZ (02": Zdzuarc! 6". Creazf United States Patent PRODUCTION OF URANIUM TUBING Edward C. Creutz, Chicago, Ill., assignor to the United States of America as represented by the United States Atomic Energy Commission Application November 30, 944, Serial No. 565,995

2 Claims. (Cl. 148-115) My invention relates to the manufacture of thin-walled uranium tubing and more particularly to methods and apparatus for hot piercing uranium in a ductile state to provide thin-walled tubes. The production of such tubes has been found to be quite difficult, and not infrequently defective tubes are produced when usual extrusion methods are used.

It is an object of my invention to provide an improved method and apparatus for forming thin-walled uranium tubes.

It is another object of my invention to provide a method and apparatus whereby uranium tubing is formed without danger of flattening or necking-in of the thin walls thereof.

In accordance with my invention 1 have found that uranium tubes may be effectively produced by piercing uranium rods or billets to form a thin-walled tube thereof while maintaining the rod at a temperature corresponding to the gamma phase of the uranium. The tubes so produced are cooled to convert the gamma-phase uranium into the beta phase with suflicient rapidity to prevent or substantially minimize deformation of the thin walls of the tube due to their partial collapse after removal from the piercing member.

Thus I work and form the uranium at a temperature in excess of 780 C. which temperature is the approximate transition temperature from the beta to the plastic gamma crystallographic phase, and thereafter cool the uranium to below about 780 C. as rapidly as possible in order to facilitate further handling.

Uranium has three crystallographic phases known as the alpha, beta and gamma phases, the beta and gamma phases being formed successively as uranium metal of the alpha phase is increased in temperature. The transition from the alpha to the beta phase occurs at approximately 650 C. and the transition from the beta to the gamma phase occurs when uranium is heated to above about 780 C. I have found that uranium is more ductile in the gamma phase than in either the alpha or beta phase, and uranium billets can be easily formed or pressed to form tubing in the gamma phase at temperatures over More particularly I raise the temperature of the uranium rod or billet to be pierced to above 780 C. and feed the billet into convex rolls of a hot piercer and force the uranium over a mandrel by a component of surfacefrictional forces such as are provided by a slight inclination of the rolls. During passage through the rolls the billet of heated uranium is rotated to restrict its diameter locally and create a torn region in the interior of the billet. As I rotate the billet, this torn region in the interior of the billet becomes defined into a hole, and a piercing mandrel is inserted into the torn region to aid in the formation of the hole thereby to control the interior size thereof and improve the inside surface of the hole to form a tube.

During the operation of shaping the tube by forcing uranium over the mandrel I preserve the plasticity of the metal by maintaining the temperature over 780? C. I have further found that after completion of the formation of the tube the plasticity of the gamma phase endangers the shape of the tube by permitting it to flatten or neck in under its own weight and become egg-shaped; to avoid such deformation, I spray a coolant on the formed uranium tubing after it has issued from the rolls and while it is in the final stages of being formed which hardens the tube by converting it into the beta and alpha crystallographic phases. Water is a satisfactory coolant for this step of forming the thin-Walled tube.

These and other objects, features and advantages of my invention will be apparent from the following detailed description of a preferred embodiment taken with the accompanying drawings in which:

Fig. 1 is a plan, view, partly in section, of my improved apparatus suitable for hot-piercing uranium rods; and,

Fig. 2 is a view in elevation from the mandrel side of the apparatus shown in Fig. 1.

In the preferred embodiment of the apparatus incorporating my invention shown in Fig 1 the piercing mechanism comprises two convex-surfaced side rolls 1 and 2, a convex-surfaced bottom roll 3 and a pointed mandrel 4. The three rolls 1, 2 and 3 are located equidistant from the point 5 of the mandrel 4 which is located at the axis of the mandrel. Suitable feeding means (not shown) are provided for bringing a billet 6 to the piercing mechanism and into contact with the rolls 1, 2 and 3. While the piercing rolls 1, 2 and 3 may be of any preferred form or type, they are shown with convex-surfaced faces and the two side rolls 1 and 2 have their axes of rotation inclined to each other and to the axis of the mandrel in the well known manner of piercing mills. The roll 3 is set so that its plane of rotation is at a slight angle to the axis of mandrel 4 and it rotates so that, at its point of tangency with billet 6, the surface of roll 3 is moving with the same direction of motion as billet 6. The rolls 1, 2 and 3 are adapted to be rotated on their axes by suitable driving connections (not shown) and rolls 1 and 2 rotate in opposite directions to turn the billet 6 as it is fed into the piercing mechanism. The inclination of rolls 1, 2 and 3 provides a component of surface-frictional forces which presses the billet 6 against the point 5 and onto the mandrel 4. The centers of the rolls 1 and 2 are above the axis of the mandrel while roll 3 is below the mandrel 4 and on the opposite side from rolls 1 and 2. Thus the force of rolls 1 and 2 applied to the billet 6 has a downward component to balance the upward thrust on mandrel 4 of roll 3. I

The billet 6 before being pierced is preferably about 20 inches long, 5.32 inches in diameter and weighs around 200 pounds. The billet 6 is preheated to a temperature sufficiently high to ensure that the temperature remains above the beta-gamma transition temperature during the tube-forming operation. Frequently it is heated for approximately two hours, being held in the neighborhood of 1020 C. for about 20 minutes, so that the uranium metal of the billet will be in the gamma phase throughout when pierced and preferably above about 950 C. To warm up the piercing point, two copper or other metal billets may be first pierced which leaves the point 5 at a temperature in the neighborhood of 700 C. On feeding the billet 6 t0 the piercing mechanism the frictional force of the inclined rolls 1, 2 and 3 rotating the billet 6 is directed axially along the billet surface and moves the billet 6 through the rolls 1, 2 and 3 and over the mandrel 4, forming the billet 6 into a tube 7. Thus the billet can be pierced to form a tube with a inchwall and a diameter of four inches. The inside surface of a tube pierced by my method is smooth. The marking on the outside surface of the tube 7 by the pressure of the rolls 1, 2 and 3 as they force the billet 6 through the piercing mechanism is determined by the degree of inclination of the rolls and the amount of pressure required to give a sufficient component to make the billet advance properly. I have found that if the inclination of the rolls 1, 2 and 3 from the normal is not substantially more than 7 degrees, the marking on the outside surface of the tube 7 may be avoided.

As shown in Fig. 2 the rolls 1 and 2 are lubricated with water sprays from nozzles 9 to prevent the uranium from sticking to the rolls. After the billet 6 has been forced over the point of the mandrel 4, the tube 7 thus formed is still in the gamma phase and continues to rotate around the mandrel under the influence of the rolls 1, Z and 3. While being formed around the mandrel and before losing the desired shape, the tube 7 is cooled by water sprayed thereon from the nozzles 8. As a result, the uranium is converted into the beta crystallographic phase, which has a sufiicient rigidity to prevent a deformation. Thus the finished uranium tube is ready for handling.

Summarizing the results, it is seen that by my method the thin-walled uranium tubing is formed without flattening or necking-in of the walls of the tube by working the uranium at a temperature in excess of 780 C. and immediately thereafter lowering the uranium temperature to below 780 C. to attain the advantages of the rigidity of uranium at the lower temperature before deformation of the tube can occur.

It will be apparent to those skilled in the art that from the principles of the invention as disclosed herein, and for that reason it is not intended that the invention should be limited other than by the scope of the appended claims.

I claim:

1. A method of producing uranium tubings by piercing billets consisting of uranium, comprising heating said uranium billets to a temperature above 780 C., forcing them over a mandrel while maintaining said elevated temperature whereby a cylindrical bore is created in said billets, cooling said tubes thus produced to a temperature below 780 C. and then removing from the mandrel.

2. A method of producing uranium tubes by piercing billets consisting of uranium, comprising heating said uranium billets to a temperature above 780 C., forcing them over a mandrel while maintaining said elevated temperature whereby a cylindrical bore is created in said billets, rapidly cooling said cylinders thus produced to a temperature below 780 C. immediately thereafter, and then removing said tubes from the mandrel.

References Cited in the file of this patent UNITED STATES PATENTS 1,993,427 Widuch Mar. 5, 1935 2,040,764 Bannister May 12, 1936 2,179,114 Browne Nov. 7, 1939 2,207,405 Jacobson July 9, 1940 OTHER REFERENCES Kroll: Zeitschrift fuer Metalkunde, vol. 28, No. 2, February 1936, page 33. 

1. A METHOD OF PRODUCING URANIUM TUBINGS BY PIERCING BILLETS CONSISTING OF URANIUM, COMPRISING HEATING SAID URANIUM BILLETS TO A TEMPERATURE ABOVE 780*C., FORCING THEM OVER A MANDREL WHILE MAINTAINING SAID ELEVATED TEMPERATURE WHEREBY A CYLINDRICA BORE IS CREATED IN SAID BILLETS, COOLING SAID TUBES THUS PRODUCED TO A TEMPERATURE BELOW 780*C. AND THEN REMOVING FROM THE MANDREL. 